Apparatus for screening liquids



' Dec. 21 1926.

1,611,739 H. F. HADFIELD APPARATUS FOR GREENING LIQUIDS Filed June 15, 1925 Patented Dec. 21, 1926.

HARRY FOSTER HADFIELD, 0F HILO, TERRITORY OF HAWAII.

APPARATUS FOR SCREENING LIQUIDS.

Application filed June 15, 1925.

The present invention relates to improve ments in an apparatus for screening liquids, and has particular reference to the cane sugar industry, although the apparatus may be used to advantage for various other purposes as, for instance, the screening of water in irrigation systems, particularly those where water is distributed over the fields by means of spray nozzles.

Referring first to the screening of sugar cane juices,Imight state in explanation of the situation, that sugar cane is first subjected to repeated crushings and hot macerations at the mill rollers whereby it is caused to release most of its sugar, and water, as well as some of its impurities consisting of gums, salts, albuminoids, dirt and small particles of insoluble matter. The insoluble matter consists chiefly of waxes and fibre (cellulose), etc. The raw cane juice resulting from this crushing and containing these impurities is weighed, limed and passed through heaters at a high temperature in order to coagulate the albuminoids, allowed to settle in settling tanks for some little time, when the top clear juice is decanted, run over screens to further purify the juice of suspended particles, and then pumped to the evaporators, while the settled impurities at the bottom of the settling tanks are run to the presses for filtering purposes.

The term clarification is generally used for the above process of removing the impure matters and suspended particles from the raw juice in order that the solution will be as near as possible a pure solution of sugar and water. However well the process of settling and decanting the clear juice is conducted, it. is impossible to prevent some of the small suspended particles from being decanted over with the juice, for the reason that their specific gravity is equal to that of the sugar solution. These tiny particles, therefore, if not prevented, find their way into the final product, sugar, not only causing trouble in the manufacture of raw sugar, but also at the refinery. Screens are in general usefor the purpose of catching the suspended particles, but the particles are so small and the screen mesh required to catch them have to be so fine, that there is not a device so far known that will successfully do this, without scraping, whereby the screens are quickly worn out, washing, whereby large quantities of Water are used, and constant attention.

Serial No. 37,276.

It is possible by my screening device, to also remove the suspended particles from the raw juice, before passing through the heaters in the process of clarification, unfortunately, the heat with the aid of the lime, which so beneficially fiocculates the soluble impurities and precipitates them, becomes detrimental to clarification in so far as it also hydrolizes the small particles of fibre, converting them into gummy substances which are soluble in the juice, causing viscous massecuites, and further difiiculties in the process of manufacture of sugar.

My screen may also successfully be used for cleaning irrigation water Where the spray system is used, especially on cane fields in which the spray nozzles with small holes are fitted to the tops of irrigating pipes some fifteen feet high.

Here it is of vital importance that the water contain no impuritiesin the way of suspended matter, since otherwise the small holes get blocked up and the sprays prevented from revolving and spraying. It is very difficult to walk through Well matured high cane for the purpose of attending to the sprays, especially when the latter are situated at the tops of one or two inch diameter water piping. The success of the irrigating system depends entirely upon the cleanliness of the irrigating water.

My screening device is adapted for screening the water before entering the spray nozzles, whether by pump or pressure, and thereby renders the process a success.

It is the object of my invention to provide a screening device that will keep out the suspended particles almost entirely from the final product without requiring the repeated cleaning of the same during the process.

The particular object of the present invention is to provide a process of and a device for screening liquids through meshed screens of any desired size to suit the particular purpose for which they are used and of any mesh so as to prevent floating particles and impurities from finding their way into the final product to be used.

The preferred form of my invention is illustrated in the accompanying drawing, in which Figure 1 shows a top plan view of the same, and

Figure 2 a side elevation of the system in which it may be used.

My device consists in the form shown of a tank 1 adapted to have the impure liquid introduced thereinto through the inlet Q'and a screen 3 disposed within the tank preferably in concentric relation thereto, so as to separate a central chamber 4 from the ren'iainder 6 of the vessel. 7

This vessel is disposed above an evaporator supply tank 7 and 'is'adapted to discharge the liquid from the central compartment 4 into'the evapiirator tank by. means of a central pipe 8. A pipe system 11 extends from the evaporator tank 7 and is suitably bent at various places so as to terminate in the center of the compartment l where it is provided with the ordinary type of spray riozzle 12 well known in the art of lawn sprays. A suitable type vof pump l8i'orms part of the pipe system and causes liquid to be pumped into the spray nozzle from the evaporator tank vfor the purpose oi centrifugally discl1arging thespray against the inside or delivery side of the screen whereby impurities tending to. lodge in the screen during the screening process are driven back so that the screen is kept clean at all times. An outlet pipe 1% connecting with the bot.- tom of the chamber :6 allows the latter to be drained at suitable intervals and leads to a mud tank, not shown in the drawing. Suitable valves 16 in the pipe system ll, 17 in the inlet pipe 2, and 18 in tlie mud tank pipe lshallow the port area 01? these pipes to be controlled.

The operation otthe device is as follows:

impure. liquid containing the suspended particles runs into, the tank 1 through the intake pipe 2. As this liquidsurrounds the inner compartment 4, it penetrates the screensleaving suspended particles on the outside thereof. In doing this it naturally would block up the screen so that the liquid would rise in tank (5 if it were not for the novel method described in and forming the principalpart, of, the present application. The liquid run into the tank. 1 would naturally overflow above the screen and the procedure would have to be stopped, the liquid run out, the screens either washed, scraped or steamed and time wasted before the operation could he proceeded with.

In my improved method the pump 13 sends the screenedjuice from the evaporator tank '7 through the revolving sprays 12 and causes the juice to be centriiugally dischargedv against the delivery side of the screen, whereby the particles tending to lodge in the outside of the screen are rethat have lodged in the screen through the same into the inner chamber 4, a result which it is the particular object of the present invention to avoid.

lllhen it is seen that tile juice in the outer 4 'ii'iartmcut (3 out us enough suspended particles so as to warrant its cleaning, the inlet pipe is closed by means oi the valve 17, the spray allowed to play until substantiah iv all the iuice in the outer chamber has filtered through the screen into the inner chamber whereupon the outlet pipe 14 is opened so as to allow the remaining mud to drain into the mud tank and the outer chamber may then be washed out with hot water which may also be drained into the mud tank.

It should be particularly understood that while I have shown only the preferred form of the invention, various changes or modifications may be made within the scope of the claims hereto attached without departing from the spirit of the invention.

'i claim:

1. A self-cleaning device of the character described comprisinga screen allowing the liquid constituent of a fluid mixture to pass therethrough while holding back solid particles contained therein, and a combinedcirculating and centrifugal means operative on the screened liquid and discharging the same against the delivery side of the screen for repelling solid particles tendingto lodge therein.

2. in a screening device of the character described, a vessel adapted to have a fluid mixture disposed therein and a screen in the vessel disposed therein and a screen in the vesseldisposed to separate a section of the vessel from the remainder thereof for allow.- ing the liquid constituent of the mixture to pass through the screen into the section while holding back the solid matter with means for circulating and centrifugally discharging the screened liquid against the delivery sideof the screen for driving solid particles tending to lodge in the screen back into the mixture.

HARRY rosrnn HAD-FIELD. 

